Empower is metamagic, so in 5e that belongs to the sorcerer too. And wizards aren't weak. They simply aren't as strong per spell given as a sorc is. But they have the advantage of having access to sooo many more spells. Which sadly doesn't help much in a crpg where the need of that many spells is low and situational.
Given that Larian manages to develop a good resting system that rewards being conservative with our resources, a wizard will be well balaced against a sorcerer as his spells will probably last over more encounters. We sorcerers burn brightly, but also burn out fast
